An automatic transmission for a vehicle changes a speed ratio according to running conditions by operating a planetary gear mechanism with an electronically controlled oil pressure system as disclosed in "Full Range Electronic Transmission RE4R01A Maintenance Guidelines (A261C07)" published by NISSAN Motor Co., Ltd. in March, 1987.
To accomplish this purpose, the oil pressure system comprises an oil pressure pump, valves which respond to electronic signals, and an accumulator.
A selector lever is provided to enable the driver to select various speed change modes, i.e. parking (P), reverse (R), neutral (N), drive (D), second speed (2), and first speed (1), etc. The selector lever is mechanically connected to a spool valve which forms part of the above-mentioned oil pressure system.
The spool valve selectively supplies a line pressure to predetermined parts of the automatic transmission from the oil pressure pump according to a spool displacement.
At the same time, a signal indicating the speed change mode is input to the electronic controller which controls the oil pressure system so that speed change control is performed according to the selected speed change mode.
This signal is output by an inhibitor switch in synchronism with the spool displacement of the spool valve.
According to the above-mentioned prior art the valves which constitute the oil pressure system are housed in a valve case installed under a transmission case which accommodates a planetary gear mechanism.
The inhibitor switch is supported by the transmission case, and is linked to the spool by a lever.
Therefore, when the automatic transmission is assembled, the relative position of the inhibitor switch and spool valve must be precisely adjusted so that the spool position of the spool valve in the valve case and the spool position signal output by the inhibitor switch supported by the transmission case precisely correspond.